1. Field of the Invention
The present invention relates to a control circuit for a digital trigger for a microelectromechanical element and a method for triggering a microelectromechanical element.
2. Description of the Related Art
Microelectromechanical systems (MEMS) are used today in micro system technology as converters of trigger signals into mechanical actions. Actuators play a major role here, in particular microelectromechanical actuators. One exemplary application involves the use of micromirror actuators (SLM, spatial light modulators) with the help of which a micromirror element or a micromirror array may be deflected in a targeted manner by rotation, tilting and shifting of light beams such as laser beams, for example.
Actuators require special and precise trigger signals to be able to ensure rapid, reproducible interference-free operation of the mechanical elements of the actuator. This makes high demands on the trigger circuits used for operation of an actuator, in particular because the space required for such triggers must remain small in the context of miniaturization of microelectromechanical components in order to keep production costs low.
Microelectromechanical elements may be operated resonantly or quasi-statically. A resonant type of operation requires operation of the microelectromechanical element on one or multiple modes of the microelectromechanical element. During quasi-static operation, however, the microelectromechanical element is also operated in frequency ranges outside of the resonant modes. It is important that preferably no frequency components of the trigger signal are in the modes during triggering since the electromechanical element might then temporarily be triggered in an unstable manner.
Triggering methods for microelectromechanical elements generally use linear drivers or digital drivers. Linear drivers may be embedded in an application-specific integrated circuit (ASIC). However, they require a relatively large area for the integration of the constituent components, such as operational amplifiers, controllers, voltage and current reference circuits, stabilization capacitors and similar components, for example. Furthermore, a digital-analog converter is needed, which may result in a complex and expensive overall system having a comparatively high energy demand.
Published German patent application document DE 10 2004 016 196 A1 describes a method for triggering an electromechanical system in which a linear driver circuit and a digital-analog converter are used.
Digital drivers usually have a simple design, are space-saving and resistant to interference. They are readily suitable for use during resonant operation. For use during quasi-static operation, however, interference components, which under some circumstances may have frequencies in the range of the resonant interference modes, must be taken into account. There is thus a demand for triggering of a microelectromechanical element using a digital driver which takes into account the aspects mentioned above.